Myopia Situation in Hong Kong School Children
According to studies from the School of Optometry in the Hong Kong Polytechnic University, the prevalence of myopia (short-sightedness) by age groups is as follows:
It can be seen that the young myopic population has been increasing rapidly and in less than 10 years, it has more than a twofold increase in the percentage of myopic children. An increase in the rate of myopia progression is also observed.
Cause of children myopia or short-sightedness
Short-sightedness occurs when distance vision is blurred but near vision is fine. When the eyeball is either too long or the eye’s refractive system is too strong, images are focussed in front of the retina causing a out-of-focus image at the retina.
Up to date, science still has not been able to provide a full explanation of what causes myopia. However, we do know that it is related to heredity, environment or life style.
For example, genetic studies have shown that if both parents are myopic, the chance of their children having myopia is about 72%. If one parent is myopic, then the chance is about 58%. If neither parent is myopic, there is still a chance of 49%. In other words, children of myopic parents are at a much higher risk for developing myopia.
The onset of myopia usually occurs between the age of 5-15 although some 10% may start after age 20. Myopia progresses as the eyeball grows longer averaging 0.75 dioptres a year until age 15-17 when it starts to slow down or stop. After age 20, the change will be minimal. Generally speaking, the earlier the onset of myopia, the more and faster myopia will progress.
The following are common methods for correcting or managing myopia:
1. Traditional glasses or contact lenses
2. Glasses or contact lenses for myopia control
Complications of Myopia
Blurred vision resulted from myopia can easily be restored by various corrective devices mentioned above. What is concerning is the increased risk of serious, sight threatening complications associated with high myopia (above -5.00D). As the eyeball becomes stretched due to increased elongation, the retina becomes thinner and weaker leading to a higher risk of retinal detachment, myopic maculopathy, cataract and glaucoma. Study results have shown that the odds ratio of retinal detachment is 21 times higher in a person with myopia of -6.00D compared to someone with zero myopia. As such, it is far more important to manage myopia in terms of prevention and control than simply to correct for it. Myopia management strategies should be advocated to correct and slow down myopia at the outset.